1. Field of the Invention
This invention relates to electrical coil bars of dynamoelectric machines, and more particularly, to means for shaping the end portions of those coil bars.
2. Description of the Prior Art
Stator windings for dynamoelectric machines such as motors and generators often include a plurality of phase coils which are each formed by inserting a plurality of axially extending conductors or coil bars in a stator core and connecting selected coil bars at their ends. Such connections are generally made in the end turn regions of the stator and are called series connections. Such series connections join circumferentially separated coil bars necessitating coil bar angular displacements in the stator end turn regions for each joined pair of coil bars. Due to considerations such as the circumferential separation between connected coil bars, space limitations in the end turn regions, and avoidance of interference with other structural elements in the stator end turn regions, the stator coil bars are frequently bent radially outwardly, circumferentially about, and finally generally parallel with the axis of rotation of the particular machine's rotatable shaft. Assembly of such bent coil bars in dynamoelectric machines results in formation of frusto-conical surfaces in the dynamoelectric machine's end turn regions.
Prior coil forming techniques included the use of concave and convex forming blocks, frequently made of wood, which provided the foundation against which the conductors or coil bars were deformed so as to properly shape them through hammering, pushing, twisting, and bending. Such coil bar formation has traditionally been accomplished manually with considerable effort and has resulted in the lack of shape uniformity among coil bars since there was no way to accurately control the manual forces being applied. Such imprecise shape duplication of coil bars causes difficulties in both winding and serially connecting the coil bars. Such difficulties can adversely affect the utilizing machine's cost and quality and the lack of shape uniformity can promote non-interchangeability of replacement parts and decreased reliability due to residual stresses imposed on the coil bars. A further disadvantage of such prior art forming blocks is the vast amount of storage space needed to house the many different sized blocks required by the different sized dynamoelectric machines during times of non-usuage.
Copending W. E. Case No. 47,316, filed Sept. 23, 1977, having Ser. No. 836,172, and assigned to the assignee of the present invention discloses an apparatus for producing coil bar shapes by wrapping them around a convex, frusto-conically shaped member. Such disclosure teaches a solid mass of material constituting the frusto-conical shape. A disadvantage in using such member is that its major and minor diameters and thus the cone angle are fixed for each frusto-conical member. Since different dynamoelectric machines have different stator sizes and different coil bar cone angles, the solid frusto-conical member disclosed in the copending application can require vast amounts of storage space between times of actual usage in forming coil bars. An additional disadvantage of the aforementioned solid forming member is that it can be used in the forming apparatus for only one size dynamoelectric machine, necessitating the forming machine's disassembly and insertion therein of another forming member whenever coil bars are to be made for a different sized dynamoelectric machine.
As such, it would be advantageous to use a coil bar forming apparatus which had an adjustable frusto-conical coil shaper which was adaptable to different size dynamoelectric machines and the coils' cone angles required therein.